[PATCH v9 2/3] kernel.h: add to_user_ptr()

[Rob Clark]

On Thu, Mar 17, 2016 at 4:22 PM, Joe Perches <joe at perches.com> wrote:
> On Thu, 2016-03-17 at 15:43 -0300, Gustavo Padovan wrote:
>> 2016-03-17 Gustavo Padovan <gustavo.padovan at collabora.co.uk>:
>> > 2016-03-17 Joe Perches <joe at perches.com>:
>> > > On Thu, 2016-03-17 at 14:30 -0300, Gustavo Padovan wrote:
>> > > >
>> > > > This function had copies in 3 different files. Unify them in
>> > > > kernel.h.
>> > > This is only used by gpu/drm.
>> > >
>> > > I think this is a poor name for a generic function
>> > > that would be in kernel.h.
>> > >
>> > > Isn't there an include file in linux/drm that's
>> > > appropriate for this.  Maybe drmP.h
>> > >
>> > > Maybe prefix this function name with drm_ too.
>> > No, the next patch adds a user to drivers/staging (which will be moved
>> > to drivers/dma-buf) soon. Maybe move to a different header in
>> > include/linux/? not sure which one.
>> >
>> > >
>> > > Also, there's this that might conflict:
>> > >
>> > > arch/powerpc/kernel/signal_32.c:#define to_user_ptr(p)          ptr_to_compat(p)
>> > > arch/powerpc/kernel/signal_32.c:#define to_user_ptr(p)          ((unsigned long)(p))
>> > Right, I'll figure out how to replace these two too.
>> The powerpc to_user_ptr has a different meaning from the one I'm adding
>> in this patch. I propose we just rename powerpc's to_user_ptr to
>> __to_user_ptr and leave the rest as is.
>
> I think that's not a good idea, and you should really check
> this concept with the powerpc folk (added to to:s and cc:ed)
>
> If it were really added, then the function meaning is incorrect.
>
> This is taking a u64, casting that to (unsigned long/uint_ptr_t),
> then converting that to a user pointer.
>
> Does that naming and use make sense on x86-32 or arm32?
>

fwiw Gustavo's version of to_user_ptr() is in use on arm32 and arm64..
Not entirely sure what doesn't make sense about it

BR,
-R